This invention relates generally to memory devices and more particularly to a high-speed non-volatile semiconductor memory device which can be switched from one state to a second significantly different state in response to an applied signal, e.g., a voltage pulse or an applied light pulse or an incident electron beam or the generation of free carriers within certain regions of the device; the device will maintain said second state for long periods of time without any sustaining voltage being applied. The memory device of the invention is capable of electrical readout, and can be used in information storage apparatus employing such elements or arrays thereof, using means for maintaining the memory devices at a temperature within a predetermined range of temperatures.